adding config files for blog post (#334)

* adding config files for blog post 

Full configuration files for blog post "Securing Kubernetes applications with AWS App Mesh and cert-manager"

* Update yelb-virtualnode-tls.yaml

removing "enforce: true" from TLS clientPolicy as it is a default

* Update yelb-gw.yaml

removing "enforce: true" from TLS clientPolicy as it is a default

* Update yelb-gw.yaml

using variables to set envoy image and NLB cert arn

* Update README.md

using variables to set envoy image and NLB cert arn

blogs/cert-manager-tls/README.md

@@ -0,0 +1,66 @@
+# Securing Kubernetes applications with AWS App Mesh and cert-manager
+
+Full configuration files for blog post [Securing Kubernetes applications with AWS App Mesh and cert-manager]()
+
+## 0. Deploy base yelb with App Mesh
+
+`kubectl apply -f yelb-base.yaml`
+
+## 1. Install cert-manager
+
+```
+kubectl create ns cert-manager
+
+helm repo add jetstack https://charts.jetstack.io
+helm repo update
+ 
+helm install \
+  cert-manager jetstack/cert-manager \
+  --namespace cert-manager \
+  --version v0.16.1 \
+  --set installCRDs=true
+```
+
+## 2. Create CA and issue certificates for microservices
+
+```
+#generate a private key
+openssl genrsa -out ca.key 2048
+ 
+#create a self signed x.509 CA certificate
+openssl req -x509 -new -key ca.key -subj "/CN=App Mesh Examples CA" -days 3650 -out ca.crt
+
+#create TLS secret
+kubectl create secret tls ca-key-pair \
+   --cert=ca.crt \
+   --key=ca.key \
+   --namespace=yelb
+
+#create CA issuer
+kubectl apply -f ca-issuer.yaml
+
+#create certificate
+kubectl apply -f yelb-cert.yaml
+```
+
+## 3. Mount certificate to microservice deployment 
+
+`kubectl apply -f yelb-deployment-secretMounts.yaml`
+
+## 4. Add TLS configuration to virtual node
+
+`kubectl apply -f yelb-virtualnode-tls.yaml`
+
+## 5. Configure encryption between external LB and App Mesh
+
+Please set `ENVOY_IMAGE` ENV variable to the correct value based on https://docs.aws.amazon.com/app-mesh/latest/userguide/envoy.html
+
+Additionally set `LB_CERT_ARN` ENV variable with your own valid arn.
+
+```
+ENVOY_IMAGE="840364872350.dkr.ecr.<region>.amazonaws.com/aws-appmesh-envoy:<version>"
+
+LB_CERT_ARN="arn:aws:acm:<region>:<account-id>:certificate/<cert-id>"
+
+sed -e "s|{{ENVOY_IMAGE}}|${ENVOY_IMAGE}|g" -e "s|{{LB_CERT_ARN}}|${LB_CERT_ARN}|g" yelb-gw.yaml | kubectl apply -f -
+```

blogs/cert-manager-tls/ca-issuer.yaml

@@ -0,0 +1,8 @@
+apiVersion: cert-manager.io/v1alpha2
+kind: Issuer
+metadata:
+  name: ca-issuer
+  namespace: yelb
+spec:
+  ca:
+    secretName: ca-key-pair